btrfs: fix NULL pointer dereference in do_abort_log_replay()

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix NULL pointer dereference in do_abort_log_replay()

Coverity reported a NULL pointer dereference issue (CID 1666756) in

do_abort_log_replay(). When btrfs_alloc_path() fails in

replay_one_buffer(), wc->subvol_path is NULL, but btrfs_abort_log_replay()

calls do_abort_log_replay() which unconditionally dereferences

wc->subvol_path when attempting to print debug information. Fix this by

adding a NULL check before dereferencing wc->subvol_path in

do_abort_log_replay().